Home automation systems have been developing for many years. Conventional applications for such systems include control of lighting, heating ventilation air conditioning (HVAC), garden sprinklers, intelligent alarm systems etc. Wireless home automation systems have gained popularity in recent years due to the relative ease of installation in comparison to many hardwired systems. Many wireless home automation systems are aimed at Do-It-Yourself customers as wireless devices that are not operated by battery only need wiring for power. The most popular application for wireless home automation system is lighting control. Among lighting control devices, wall switch controlled lighting devices are the most popular. These switches are widely used in both residential and commercial buildings alike. A conventional method for converting a traditional wall switch to be controlled wirelessly requires a wall switch module. Such wall switch modules can replace existing wall switches.
For a conventional wall switch module, power may be supplied by existing wiring in an electrical switch box. In general, only two wires are fed into an electrical switch box, a live feed from the AC power supply to the switch and a wire extending from the switch to the load. In most cases, the other side of the load is connected directly to the neutral of the AC power supply without returning to the switch box. FIG. 1 illustrates a circuit diagram of a conventional wall switch. As shown in FIG. 1, switch 101 is connected to live terminal 103 of an AC power supply and load 105, in this instance a light bulb. Neutral 107 is connected to the other terminal of load 105 and is not located inside the wall switch box. Most electrical systems include an earth ground connection 109 to the electrical switch box containing the switch 101, mainly for safety considerations and to satisfy electrical code requirements.
Some conventional electrical switch boxes are only provided with a live feed to supply the wall switch. As a result, a neutral connection may not be provided to complete the circuit with the electrical switch box. For existing structures, it may be very costly to run neutral connections to electrical switch boxes when a neutral wire is not initially installed due to limited access to the existing wiring. Therefore, there is a need for a wall switch module that can operate using existing wiring in an electrical switch box without a neutral connection.
Conventional devices and methods to provide lighting control products for wall switch control without a neutral connection are available, but are limited in operation. For example, one conventional approach is based on a wall switch module simulating a load, wherein the load changes depend on the status of the connected load. When the lighting fixture is off, internal impedance of the wall switch may become very high in comparison to the lighting fixture. This may result in a decrease in current through the wall switch internal load which causes the lighting fixture to be off. If the lighting fixture is turned on, the wall switch internal impedance may become much less than the impedance of the lighting fixture and can result in enough power to turn on the fixture. One major limitation with this approach is that the actual connected load must be incandescent loading, such as a tungsten light bulb. This conventional method will not work with compact fluorescent lamps (CFL) or fluorescent lighting. CFL exhibit a very high impedance when a lighting fixture is turned off, which is also much higher than incandescent lamps. Thus, conventional wall switch control devices and methods without a neutral connection do not provide enough current to operate the electronic circuitry inside the wall switch control module. An additional drawback is that some countries have proposed rules that will ban tungsten bulbs from the marketplace in the near future. Therefore, there is a need for a wall switch control module that operates CFL and/or fluorescent light.
Conventional electrical switch boxes additionally fail to distinguish between different types of loads. For example, a conventional method to control brightness for an incandescent load, such as dimming or brightening the light bulb, employs triac output control. The conventional triggering methods for incandescent loads, however, may not be suitable for CFL loads. For example, the conventional methods for triggering an incandescent load may not be able to turn on CFL load properly and may result in undesired flashing. Thus, the aforementioned conventional method for triac control is further not suitable as most CFL loads are non-dimmable.
Thus, there is a need for a control switch to provide one or more of detection of the connected load (e.g., incandescent load and CFL load), a control switch which can block and/or limit dimming operation to on and off only depending on load type and different triac operation for different loads.